The present invention relates in general to remote convenience and security systems for automotive vehicles, and, more specifically, to a wireless communication system for integrating functions of a two-way remote keyless entry system and a passive entry system.
Remote keyless entry (RKE) systems for vehicles have been in use for many years. These systems provide safety and convenience for a user entering or exiting a vehicle. Some of the typical features offered by these systems allow the user to lock/unlock doors and arm/disarm auto theft systems in a remote manner. In addition, remote starting of the engine and remote control of the climate control temperature setting after starting are commercially available. Typical RKE systems utilize a key fob with a radiofrequency (RF) transmitter which transmits to a base station in the vehicle. When the user is within range, the user actuates a corresponding button on the key fob to send a lock, unlock, or engine start command, for example. Two-way communication is typically implemented in remote start systems so that the user carrying the portable fob can be informed of the status of the vehicle (e.g., engine running status, door lock status, and temperature status). Thus, a two-way fob includes a visual display (e.g., LED indicator lights or an LCD graphical display panel) to convey the information to the user.
One disadvantage of this type of system is that the user must manually actuate the key fob to achieve the desired result. In an attempt to eliminate this disadvantage, passive entry systems, which operate in a hands-free manner, are being introduced. In order to avoid excessive battery consumption by periodic radio transmission from the fob, the approach of the user to the vehicle is usually sensed by the vehicle, which then wakes up the fob to perform a security check before actuating a passive entry function. Is it known, for example, to sense the presence of a user who is attempting entry into a locked vehicle via a particular door by detecting the lifting of the door handle. Using a low frequency (LF) wireless signal, the vehicle then interrogates the area around the door for a key fob containing a valid security ID code.
Passive entry communication operates over a much shorter range than RKE communication (e.g., 1 meter as opposed to 30 meters). Therefore, an LF signal (e.g., 134 kHz) is used for passive entry while a much higher frequency RF signal (e.g., 315 MHz or 433 MHz) is used for RKE since the LF signal decays over a shorter range. In addition, transponders operative at LF frequencies are readily available. As used herein, LF frequencies range from about 30 kHz to about 300 kHz. RF signals used in RKE systems are typically in the UHF band from about 300 MHz to about 3 GHz.
Security ID codes for validating a particular fob for accessing a passive entry function typically include rolling code encryption in order to deter code grabbing and relay attacks by potential thieves. Due to the low frequency signals used by passive entry systems, the exchanging of challenge and response signals used by a rolling code system has transpired using a data rate which is lower than the data rate for performing similar exchanges by RKE systems using RF signals. A slow data rate can result in problems because it is necessary to quickly validate a fob carried by the user after beginning to lift a door handle so that a door unlock mechanism can be activated before the door handle moves beyond an appropriate position.